Vpliv hidrodinamske kavitacije na odpadno blato in njen potencial za izboljšanje procesa anaerobne presnove : doktorska disertacija

Blagojevič, Marko (author), Kolbl Repinc, Sabina (mentor), Bizjan, Benjamin (comentor), Novak, Uroš (comentor), Petkovšek, Martin (member of the commission for defense), Škerjanec, Mateja (member of the commission for defense), Podmirseg, Sabine M. (member of the commission for defense)

V okviru doktorske naloge smo raziskali vpliv hidrodinamske kavitacije (HK) na tri različne vzorce odpadnega blata (OB), pridobljene iz komunalnih čistilnih naprav (ČN), z uporabo dveh rotacijskih generatorjev hidrodinamske kavitacije (RGHK). Namen raziskave je bil izboljšati proizvodnjo metana v procesu anaerobne presnove (AP). Prvi sistem, t.i. pinski RGHK (PD-RGHK), je bil preizkušen z uporabo petih različnih konfiguracij rotor-stator na kompleksni mešanici OB (SS 4,7 %), ki je vključevala predzgoščeno primarno blato, presežno aktivno blato (PAB), maščobe, olja in masti, greznično blato iz manjših ČN ter bolnišnično odpadno vodo. Istih pet konfiguracij PD-RGHK je bilo nato preizkušenih na bolj enotnem vzorcu PAB (SS 0,7 %) iz Centralne ČN Ljubljana. Na koncu je bil preizkušen še nov optimiziran PD-RGHK (OPD-RGHK) na PAB iz Centralne ČN Domžale-Kamnik, pri štirih izbranih številih kavitacijskih prehodov (Np) = 5, 15, 30 in 100. Fizikalno-kemijska analiza je pokazale povečanje topnih komponent po obdelavi s HK, pri čemer sta se vrednosti topne KPK in TOC dosledno povečali v vseh treh poskusih. Rezultati meritev časa kapilarnega vleka (CST) so pokazali poslabšano filtracijsko sposobnost OB po obdelavi, medtem ko se je površinska napetost (IFT) pri uporabi PD-RGHK povečala, ob uporabi OPD-RGHK pa zmanjšala. Obe zasnovi RGHK sta učinkovito zmanjšali velikost delcev OB. Spektralna analiza UV-Vis je pokazala spremembe v raztopljeni organski snovi, vključno s spremembami v aromatičnosti, humifikaciji in velikosti molekul, medtem ko je FTIR analiza potrdila poškodbe celičnih sten mikroorganizmov. Univariatna korelacijska analiza po Pearsonu (r) in Spearmanu (?) je nakazala, da je bila mikrobna liza pretežno posledica hidrodinamskih sil, ob morebitnem sinergijskem vplivu radikalov, ki je prispeval k oksidaciji organske snovi. Reološke meritve so pokazale znižano navidezno viskoznost pri nizkih strižnih napetostih ter spremembe v viskoelastičnih lastnostih. Čeprav je bila dezintegracija OB potrjena v vseh treh poskusih, je bila povečana proizvodnja metana opažena le pri uporabi OPD-RGHK, pri čemer so bile dosežene izboljšave v višini 11,8 %, 17,4 % in 26,3 % pri Np = 15, 30 in 100. Ti rezultati nakazujejo, da je uporaba OPD-RGHK obetavna tehnologija za izboljšanje razgradnje PAB in učinkovitosti AP, z visokim potencialom za nadgradnjo in uporabo na industrijskem modelnem merilu.

• Language: English
• Keywords: built environment, doctoral dissertation, hydrodynamic cavitation, rotary generator of hydrodynamic cavitation, waste sludge, anaerobic digestion, methane production, rheology, UV-Vis, FTIR
• Work type: Doctoral dissertation
• Typology: 2.08 - Doctoral Dissertation
• Organization: FGG - Faculty of Civil and Geodetic Engineering
• Place of publishing: Ljubljana
• Publisher: [M. Blagojevič]
• Year: 2025
• Number of pages: LII, 210 str.
• PID: 20.500.12556/RUL-174222
• UDC: 628.336:66.098.4:620.193.16(043.3)
• COBISS.SI-ID: 251581443
• Publication date in RUL: 30.09.2025

Secondary language

• Language: Slovenian
• Title: The effect of hydrodynamic cavitation on waste sludge and its potential for improvement of the anaerobic digestion process : doctoral dissertation

Abstract

This thesis investigated the effect of hydrodynamic cavitation (HC) treatment on three different waste sludge (WS) samples sourced from three wastewater treatment plants (WWTPs), using two rotary generators of hydrodynamic cavitation (RGHC), with the aim of improving methane production in the anaerobic digestion (AD) process. The first system, a pinned disc RGHC (PD-RGHC), was tested using five different rotor-stator configurations on a complex WS mixture (TS 4.7 %) comprising pre-thickened primary sludge and waste activated sludge (WAS), with added fat, oil, and grease, septic sludge from smaller WWTPs, and hospital water. The same five PD-RGHC configurations were then applied to a more uniform WAS sample (TS 0.7 %) from Central WWTP Ljubljana. Lastly, new optimised PD-RGHC (OPD-RGHC) was evaluated on WAS from Central WWTP Domžale-Kamnik at selected cavitation passes (Np) of 5, 15, 30 and 100. Physicochemical analyses revealed an increase in several soluble components following HC treatment, with consistent rises in sCOD and sTOC across all three experiments. Capillary suction time (CST) tests indicated worsened filterability after treatment, while interfacial tension (IFT) increased with PD-RGHC treatment and decreased with OPD-RGHC. Both RGHC systems effectively reduced WS particle size. UV-Vis spectral analysis showed changes in dissolved organic matter, including shifts in aromaticity, humification, and molecular size, while FTIR revealed microbial cell wall damage. Univariate Pearson’s (r) and Spearman’s (ρ) correlation analysis suggested that hydrodynamic forces primarily drove microbial lysis, with a possible synergistic contribution from radicals involved in the oxidation of organic matter. Rheological measurements showed reduced apparent viscosity at low shear stresses and alterations in viscoelastic properties. Although WS disintegration was successful in all cases, increased methane production was observed only with OPD-RGHC treatment, achieving improvements of 11.8, 17.4, and 26.3 % at Np = 15, 30, and 100, respectively. These findings demonstrate that OPD-RGHC is a promising technology for enhancing WAS disintegration and AD performance and holds strong potential for scale-up.

• Keywords: doktorske disertacije, grajeno okolje, hidrodinamska kavitacija, rotacijski generator hidrodinamske kavitacije, odpadno blato, anaerobna presnova, proizvodnja metana, reologija, UV-Vis, FTIR